Recently there has been great interest in the field of integrated optics, which field includes the fabrication of a variety of optical devices from certain semiconductive materials, such as gallium arsenide. Gallium arsenide has an energy bandgap which is suitable for the transmission of light wavelengths greater than approximately 9000A, and this material is therefore of substantial interest in the fabrication of a variety of integrated light propagating structures. These structures include such optical components as light guides, light modulators, directional couplers, optical polarizers, and other similar devices. A general discussion of this subject may be found in a published article entitled "Integrated Optics -- An Introduction" by S. E. Miller in the Bell System Technical Journal (BSTJ) September 1969, Vol. 48, pages 2059-2069.